(child theme 2012) Changing to Google Webfont font/size/color

I am trying to change the font on my site. I am trying to use “the girl next door” google webfont. Ideally, I would like to have my main color text available in two sizes 16px & 20px then I would like a 18px in yellow and a 18px in red.

I have very limited css knowledge. I have already attempted to create a rule through the editor. that didn’t work. So, I’m wondering if I should copy the css file from my parent theme into my child theme css file?

The use of Open Sans by default is localized. For languages that use
* characters not supported by the font, the font can be disabled.
*
* To disable in a child theme, use wp_dequeue_style()
* function mytheme_dequeue_fonts() {
* wp_dequeue_style( ‘twentytwelve-fonts’ );
* }
* add_action( ‘wp_enqueue_scripts’, ‘mytheme_dequeue_fonts’, 11 );
*/